This script hangs (Windows XP), not under Solaris for example:
When removing the '-channel' option it's ok ...
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package require http
set f [open abc.txt w]
::http::geturl http://www.google.com/ -channel $f
close $f

This appears to be the same issue as desccribed in Tcl bug #719790:
http://sourceforge.net/tracker/?func=detail&aid=719790&group_id=10894&atid=110894
I don't know how to fix it, nor even exactly where the problem is... :(